A non-aqueous liquid composition with an ionic character resulting from the contacting of at least one alkylaluminum dihalide with at least one quaternary ammonium halide and/or at least one quaternary phosphonium halide, said composition being liquid below 80°C, for example, between -70° and +40°C, is useful as a solvent of catalysts for the dimerization, codimerization and oligomerization of olefins.
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15. A solution comprising at least one complex of a transition metal, dissolved in a non-aqueous liquid composition with an ionic character resulting from the contacting of at least one alkylaluminum dihalide with at least one quaternary ammonium halide and/or at least one quaternary phosphonium halide, said composition being liquid below about 80° C.
1. A process for dimerizing, codimerizing, or oligomerizing at least one olefin, wherein said olefin is contacted with at least one nickel complex, said complex being present in a non-aqueous liquid composition with an ionic character resulting from the contacting of at least one alkylaluminum dihalide with at least one quaternary ammonium halide and/or at least one quaternary phosphonium halide, said composition being liquid below about 80°C
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The present invention relates to a non aqueous liquid composition with an ionic character resulting from the contacting of at least one alkylaluminum dihalide with at least one quaternary ammonium halide or/and at least one quaternary phosphonium halide, said composition being liquid below about 80°C and preferably at temperatures lower than or equal to about 40°C.
The object of the present invention is also the use of said liquid composition as a solvent (notably for catalysts).
Only few non aqueous ionic compositions which are liquid below the room temperature and one constituent of which is soluble in aliphatic hydrocarbons are known. Those which have been studied most are formed by the mixing of aluminum trichloride or tribromide with N-alkylpyridinium and N,N'-dialkyl imidazolium chlorides or bromides. These liquid ionic compositions are called "molten salts" (C. H.. HUSSEY, Advances in Molten Salts Chemistry, Vol.5, p.185, Elsevier, New-York, 1983).
The use of these molten salts as solvents and cocatalysts for the dimerization or codimerization reaction of olefins catalyzed by nickel cationic complexes comprising a nickel-carbon or a nickel-hydrogen bond has also been described in French patent 2,611,700.
It has now been discovered that the contacting (in any order) of at least one alkylaluminum dihalide (for example a dichloride or a dibromide) with at least one quaternary ammonium halide (for example a chloride or a bromide) or/and at least one quaternary phosphonium halide (for example a chloride or a bromide) and also possibly with at least one aluminum trihalide (for example an aluminum trichloride or tribromide) leads to a non aqueous liquid composition with an ionic character, said composition being liquid below about 80°C (for example between about -70°C and about +80°C), preferably at temperatures lower than or equal to about 40°C (for example between about -70°C and about +40°C) and, more preferably, at temperatures lower than or equal to about -20°C (for example between about -70°C and about -20°C). Besides, said liquid composition is stable with respect to time.
The alkylaluminum dihalides that can be used within the scope of the invention preferably correspond to the general formula Al2 X4 R2, where each X represents a halogen, selected for example from chlorine and bromine, each R represents a hydrocarbyl remainder comprising 1 to 12 atoms of carbon, aromatic or aliphatic, with a branched or a linear chain. As examples of such compounds, dichloromethylaluminum (common name of tetrachlorodimethyl-dialuminum of formula Al2 Cl4 (CH3)2), dibromomethylaluminum (Al2 Br4 (CH3)2), dichloroethylaluminum, dibromoethyl-aluminum, dichloro n-hexylaluminum, dichloroisobutylaluminum can be cited. One or several of these compounds can be used.
The quaternary ammonium halides and the quaternary phosphonium halides which can be utilized within the scope of the invention preferably correspond to the respective general formulas NR1 R2 R3 R4 X and PR1 P2 P3 P4 X, where X represents a halogen, selected for example from chlorine and bromine, R1, R2, R3 and R4, identical or different, representing each an alkyl group, aliphatic (saturated or unsaturated) or aromatic, comprising 1 to 12 atoms of carbon. These groups R1, R2, R3 and R4 can also form a cycle with the atom of nitrogen or of phosphorus; thus, R1 and R2 can form together an alkylene remainder with 4 to 10 atoms of carbon, R3 and R4 being defined as previously. The ammonium halides and the phosphonium halides can be formed by at least one nitrogenated or phosphorated heterocycle comprising 1, 2 or 3 atoms of nitrogen or of phosphorus. As examples of ammonium or phosphonium halides, tetrabutylphosphonium chloride, tetrabutylphosphonium bromide, N-butylpyridinium chloride, ethylpyridinium bromide, 1-methyl chloride 3-butyl imidazolium, 1-methyl chloride 3-ethyl imidazolium can be cited. One or several of these compounds can be utilized.
The compounds going into the composition according to the invention can be mixed in any order. The mixing can be performed by a simple contacting of said compounds, followed by stirring, until a homogenous liquid phase is obtained (that is to say the liquid composition according to the invention). The mixing can also be advantageously carried out in the presence of a saturated aliphatic hydrocarbonated solvent which dissolves for example the alkylaluminum dihalide(s); in this case, after obtaining two limpid liquid phases, the supernatant phase mainly consisting of the hydrocarbonated solvent is removed so that only the liquid composition according to the invention remains.
The relative proportions of the compounds going into the composition according to the invention depend on the properties, both chemical and physical, which are wanted for the composition according to the invention. When the number N1 of the moles of alkylaluminum dihalide(s), and possibly of aluminium trihalide(s), counted in atoms of aluminium equivalents, equals the number N2 of moles of quaternary ammonium halide(s) or/and quaternary phosphonium halide(s), counted in atoms of halides equivalents, the obtained liquid composition is called "neutral"; if N1 is higher than N2, the obtained liquid composition is called "acid"; if N1 is smaller than N2, the obtained liquid composition is called "basic".
The liquid compositions (or "molten salts") according to the present invention can be used as solvents (notably for catalysts).
It is thus possible to dissolve in these "molten salts" cationic complexes of transition metals, such as ∂Cr(C6 H5)2 [+, ∂Re(CO)5 (NS)[2+, ∂Fe(fulvene)2 [2+, ∂Ru(CH3 CN)3 (C6 H6)[2+, ∂Ru(grit)[2+, ∂(C5 H5)Rh(C6 H6)[2 30 , anionic complexes, such as ∂NiCl4 [2-, ∂NiBr3 P(C6 H5)3 [-, neutral complexes, such as Ni(C5 H7 O2)2 (nickel acetylacetonate), (NiCl2 ·2PBu3). The neutral complexes can then also be converted into complexes with an ionic character in the basic "molten salts" and of a cationic character in the acid "molten salts"; the nickel acetylacetonate introduced into the liquid basic "molten salt" consisting of 1 mole of 1-methyl chloride 3-butyl imidazolium and 0.9 mole of dichlorethylaluminum is thus quantitatively converted into a [NiCl4 [2- complex.
The liquid compositions (or "molten salts") according to the invention can also be used as solvents for catalysts, for example catalysts based on complexes of transition metals, notably for dimerization, codimerization or oligomerization reactions, such as nickel complexes. In this case, the use of complexes is no longer limited, as in French patent 2,611,700, to the complexes already comprising at least one transition metal-carbon or transition metal-hydrogen bond, or to complexes with a low degree of oxidation, but to the major part of the complexes.
The catalysts which can thus be used in a liquid composition (or "molten salt") according to the invention for the dimerization, codimerization or oligomerization of olefins are any nickel complexes, except nickel complexes solvated by compounds having active protons such as water, alcohols, organic acids, ammonia. As examples of such complexes for said reactions, nickel acetylacetonate, halide or nickel sulfate complexes such as (NiCl2,2 pyridine), (NiCl2,2PiPr3), (NiBr2,2PBu3), (NiSO4, 2PBu3), nickel octanoate nickel alcoholates can be cited. The nickel compounds described in French patent 2,611,700 can also be used, which comprise at least one nickel-carbon or nickel-hydrogen bond, or which have a valence smaller than 2; as examples of such compounds, nickel biscyclooctadiene, methallylnickel chloride, bisallylnickel, allylnickel chloride, allylnickel bromide can be cited.
The amount of nickel complex(es) contained in the "molten salt" according to the invention, for the dimerization, codimerization or oligomerization of olefins, generally ranges from 0.01 m mole.1-1 to 2 moles.1-1, preferably from 0.1 to 100 m moles.1-1 ; the optimum proportion depends on the nature of the nickel complex and on the composition of the "molten salt" according to the invention. The "acid" field of the "molten salt" will be preferably considered and the amount of complex will be adjusted to the excess molar fraction of alkylaluminum dihalide(s) contained in the "molten salt".
Generally speaking, the olefins that are likely to be dimerized, codimerized or oligomerized by the catalyst(s) contained in a "molten salt" according to the invention are the same as those which are dimerized by the nickel-based catalysts used in a hydrocarbonated or halogeno-hydrocarbonated medium, for example ethylene, propylene, 1-and 2-butenes, styrene. To perform the reaction, the olefin is contacted with the "molten salt" phase containing the nickel complex(es) and an efficient phase transfer is preferably achieved by means of a strong stirring. At the end of the reaction, the phases are separated by any appropriate means; for example, the mixture is decanted with the upper phase consisting of the dimers, the codimers and/or the oligomers being withdrawn. The operation can then be repeated by introducing a new feedstock of olefin(s). It can also be operated continuously, that is to say by supplying the medium with olefin(s) and continuously withdrawing the phase consisting of the dimers, the codimers and/or the oligomers as they form, while making sure to make, inside or outside the reactor, a zone allowing the decanting of the two liquid phases.
The temperature at which the dimerization, codimerization or oligomerization reaction takes place can be as low as allowed by the composition of the "molten salt" and the catalyst activity, for example -50°C to +80°C
The pressure is generally maintained between 0.01 and 10 MPa, high pressures being particularly utilized for ethylene.
As for the nickel catalysts used as purely organic solvents, they are it is usually protected from oxygen and humidity.
The following examples illustrate the invention without however limiting its scope. What will be called "content" of the liquid composition (or "molten salt") is the molar fraction of aluminum compound(s); for example, a liquid composition containing 0.5 mole of aluminum compound(s) for 1 mole of the sum of the constituents of said composition will have a content of 0.5 N.
PAC Preparation of a liquid composition according to the invention9.74 g (33 mmoles) of PBu4 Cl (tetrabutylphosphonium chloride) and 15 ml of heptane are introduced into a Schlenk tube free from air and humidity; then, after the suspension has been cooled down to -20° C., 8 ml (6.46 g) of a solution of 50 % by weight of dichloroethylaluminum (i.e. 25.4 milliequivalents of atoms of aluminum) in hexane are added. The obtained mixture is then heated up to about 30°C
The forming of two limpid liquid phases is then observed, the hydrocarbonated supernatant phase containing no chlorinated compound and being then removed.
The lower homogenous liquid phase consists of a composition which is liquid at the room temperature and which shows a content of 0.43 N.
PAC Preparation of a liquid composition according to the invention.8.38 g (48.1 mmoles) of 1-methyl chloride 3-butyl imidazolium are introduced into a Schlenk tube free from air and humidity. Then, after cooling the suspension down to -20°C, 11.8 ml (9.56 g) of a solution of 50 % by weight of dichloroethylaluminum (i.e. 37.6 milliequivalents of atoms of aluminum) in hexane are added. The obtained mixture is then heated up to about 30°C
The forming of two limpid liquid phases can then be observed.
After removing the hydrocarbonated supernatant phase, a liquid composition with a content of 0.44 N, and which is still liquid at -30°C, is collected.
PAC Preparation of a liquid composition according to the invention2.23 g (7.55 mmoles) of PBu4 Cl and 15 ml of heptane are introduced into a Schlenk tube free from air and humidity; then, after cooling the suspension down to -20°C, 2.3 ml (1.84 g) of a solution of 50 % by weight of dichloroethylaluminum (i.e. 7.1 milliequivalents of atoms of aluminum) in hexane are added. The obtained mixture is heated up to about 30°C
The forming of two limpid liquid phases can then be observed.
After removing the hydrocarbonated supernatant phase, a liquid composition with a content of 0.66 N, and which is still liquid at +30°C, is gathered.
PAC Preparation of a liquid composition according to the invention5.1 g (29.3 mmoles) of 1-methyl chloride 3-butyl imidazolium are introduced into a Schlenk tube free from air and humidity. Then, after cooling the suspension down to -20°C, 7 ml (5.65 g) of a solution of 50 % by weight of dichloroethylaluminum (i.e. 22.2 milliequivalents of atoms of aluminum) in hexane are added. The obtained mixture is then heated up to about 30°C
The forming of two limpid liquid phases can then be observed.
After removing the hydrocarbonated supernatant phase, a liquid composition with a content of 0.60 N, and which is still liquid at -50°C, is gathered.
PAC Dimerization test according to the invention0.125 g (0.23 mmoles) of the (NiCl2,2PBu3) complex, 10 g of heptane, then 5 g of a liquid composition consisting of tetrabutyl phosphonium chloride and of dichloroethylaluminum with a content of 0.65 N are introduced into a 250 ml-steel reactor free from air and humidity.
It is then pressurized at 0.5 MPa of propylene and the mixture is brought to about 60°C
After two hours of stirring, 30 g of propylene oligomers consisting of 85 % of isohexenes are gathered.
PAC Dimerization test according to the invention0.26 g (1.0 mmole) of anhydrous nickel acetylacetonate, 9 g of heptane, then 5 g of a liquid composition consisting of 1-methyl chloride 3-butyl imidazolium and of dichloroethylaluminum with a content of 0.64 N are introduced into a 250 ml-steel reactor free from air and humidity.
It is then pressurized at 0.5 MPa of propylene and the mixture is brought to about 60°C
After two hours of stirring, 9 g of propylene oligomers consisting of 82 % of isohexenes are gathered.
0.024 millimole of the (NiCl2.2Pir3) complex, 3 ml of heptane and 2 ml of a molten salt 0.7 N consisting of a mixture of dichloroethylaluminum and of 1-methyl chloride 3-butyl imidazolium are successively introduced into a double-walled glass reactor containing a bar magnet, free from air and humidity and maintained at -15+ C. Gaseous dimers have been formed, 76 % of which consisting of 2,3dimethyl butenes.
Commereuc, Dominique, Olivier, Helene, Saussine, Lucien, Chauvin, Yves, Guibard, Isabelle, Hirschauer, Andre
| Patent | Priority | Assignee | Title |
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| 11123721, | Jun 07 2016 | UOP LLC | Trialkylphosphonium ionic liquids, methods of making, and alkylation processes using trialkylphosphonium ionic liquids |
| 5525567, | Jan 26 1994 | Institut Francais du Petrole | Catalytic composition and olefin disproportion process |
| 5536689, | Sep 22 1993 | Institut Francais du Petrole | Catalytic composition and a process for the dimerization of olefins |
| 5550306, | Sep 22 1993 | Institut Francais du Petrole | Catalytic process for the dimerization of olefins |
| 5675051, | Jan 26 1994 | Institut Francais du Petrole | Catalytic composition and olefin disproportion process |
| 5731101, | Jul 22 1996 | Akzo Nobel NV | Low temperature ionic liquids |
| 6040263, | Jun 16 1995 | Institut Francais du Petrole | Catalytic composition based on transition metal complexes, and a process for the hydrogenation of unsaturated compounds |
| 6284937, | May 27 1997 | Institut Francais du Petrole | Process and unit for carrying out a reaction on an organic feed, such as dimerisation or metathesis, in the presence of a polar phase containing a catalyst |
| 6630112, | May 27 1997 | Institut Français du Pétrole | Process and unit for carrying out a reaction on an organic feed, such as dimerization or metathesis, in the presence of a polar phase containing a catalyst |
| 6756500, | Mar 05 1999 | LANXESS Deutschland GmbH | α,ω-Diene metathesis in the presence of ionic liquids |
| 6911410, | Feb 04 2002 | Institut Francais du Petrole | Catalyst composition containing an aluminoxane for dimerizing, co-dimerizing and oligomerizing olefins |
| 6951831, | Feb 04 2002 | Institut Francais du Petrole | Catalyst composition for dimerizing, co-dimerizing, oligomerizing and polymerizing olefins |
| 7053261, | Mar 22 2002 | Haldor Topsoe A/S | Process for paraffin hydrocarbon isomerization and composite catalyst therefore |
| 7256152, | Aug 31 2001 | Institut Francais du Petrole | Composition of catalyst and solvent and catalysis processes using this composition |
| 7495144, | Mar 24 2006 | Chevron U.S.A. Inc. | Alkylation process using an alkyl halide promoted ionic liquid catalyst |
| 7531707, | Dec 13 2006 | CHEVRON U S A INC | Alkylation process using an alkyl halide promoted ionic liquid catalyst |
| 7553999, | Dec 14 2006 | Chevron U.S.A. Inc. | Isomerization of butene in the ionic liquid-catalyzed alkylation of light isoparaffins and olefins |
| 7651970, | Dec 20 2005 | Chevron U.S.A. Inc. | Regeneration of ionic liquid catalyst by hydrogenation using a metal or metal alloy catalyst |
| 7666811, | Dec 20 2005 | Chevron U.S.A. Inc. | Ionic liquid catalyst having enhanced activity |
| 7674739, | Apr 21 2006 | Chevron U.S.A. Inc. | Regeneration of ionic liquid catalyst using a metal in the absence of added hydrogen |
| 7674740, | Dec 20 2005 | Chevron U.S.A. Inc. | Regeneration of ionic liquid catalysts |
| 7678727, | Dec 20 2005 | Chevron U.S.A. Inc. | Regeneration of ionic catalyst by hydrogenation using a homogeneous catalyst |
| 7691771, | Dec 20 2005 | Chevron U.S.A. Inc. | Regeneration of ionic liquid catalyst by hydrogenation using a supported catalyst |
| 7727925, | Dec 20 2005 | Chevron U.S.A. Inc. | Regeneration of ionic liquid catalyst by hydrogenation using metal and acid |
| 7732363, | Dec 20 2005 | CHEVRON U S A INC | Regeneration of acidic catalysts |
| 7732364, | Dec 28 2007 | CHEVRON U S A INC | Process for ionic liquid catalyst regeneration |
| 7737067, | Dec 20 2005 | Chevron U.S.A. Inc. | Regeneration of ionic liquid catalyst |
| 7754636, | Dec 19 2007 | CHEVRON U S A INC | Removal of excess metal halides from regenerated ionic liquid catalysts |
| 7807597, | Apr 08 2008 | Chevron U.S.A. Inc. | Regeneration of ionic liquid catalyst using a regeneration metal in the presence of added hydrogen |
| 7825055, | Apr 21 2006 | Chevron U.S.A. Inc. | Regeneration of ionic liquid catalyst using a regeneration metal in the presence of added hydrogen |
| 7884045, | Dec 20 2005 | CHEVRON U S A INC | Regeneration of ionic liquid catalyst and recovery of an oil |
| 7915468, | Dec 14 2006 | Chevron U.S.A. Inc. | Isomerization of butene in the ionic liquid-catalyzed alkylation of light isoparaffins and olefins |
| 7955999, | Dec 28 2007 | CHEVRON U S A INC | System and apparatus for ionic liquid catalyst regeneration |
| 7956002, | Dec 20 2005 | Chevron U.S.A. | Ionic liquid catalyst regenerated using a regeneration metal in the presence of added hydrogen |
| 7988747, | Oct 31 2007 | CHEVRON U S A INC | Production of low sulphur alkylate gasoline fuel |
| 8012899, | Dec 23 2008 | CHEVRON U S A INC | Recycling of ionic liquid catalyst |
| 8088338, | Dec 28 2007 | Chevron U.S.A. Inc. | System and apparatus for ionic liquid catalyst regeneration |
| 8187993, | Nov 03 2009 | Chevron U.S.A. Inc.; CHEVRON U S A INC | Methods and compositions for stabilizing catalytic processes |
| 8187994, | Nov 03 2009 | Chevron U.S.A. Inc.; CHEVRON U S A INC | Methods and compositions for stabilizing catalytic processes |
| 8198494, | Dec 14 2006 | Chevron U.S.A. Inc. | Process for producing alkylate with an increased RON |
| 8871954, | Jan 10 2011 | Reliance Industries Limited | Process for the preparation of alditol acetals |
| 8888993, | Jul 30 2010 | Chevron U.S.A. Inc. | Treatment of a hydrocarbon feed |
| 8969595, | Jan 10 2011 | Reliance Industries Limited | Method of making diacetal compound in aqueous medium |
| 9018431, | Apr 09 2009 | SABIC GLOBAL TECHNOLOGIES B V | Catalyst composition and process for oligomerization of ethylene |
| 9029575, | Jan 10 2011 | Reliance Industries Limited | Process for preparation of acetals |
| 9120809, | Jan 10 2011 | Reliance Industries Limited | Process for preparing alditol acetals |
| 9328296, | Mar 28 2014 | UOP LLC | Method for recovering entrained ionic liquid from an ionic liquid immiscible phase |
| 9416071, | May 06 2014 | UOP LLC | Hydrocarbon conversion processes using lactamium-based ionic liquids |
| Patent | Priority | Assignee | Title |
| 3418216, | |||
| 3558519, | |||
| 4283305, | Dec 11 1978 | Institut Francais du Petrole | Catalyst composition and its use for oligomerizing olefins |
| 4816610, | Feb 12 1988 | Neste OY | Procedure for manufacturing short-chain linear α-olefines from ethylene |
| 4992610, | Feb 29 1988 | Sumitomo Chemical Company, Limited | Dimerization of lower α-olefins |
| JP20289, |
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